Colloid transfer process



Feb. 1, 1966 E. c. YACKEL ETAL COLLOID TRANSFER PROCESS Filed Aug. 20, 1962 FILM OR PAPER SUPPORT F'G EXPOSED a TANNING ll DEvELoPED EMULSION LAYER SILvER IMAGE IN TANNED coLLoID l4 TRANSFERRED STRATUM OF uNExPosED X FlG. 2 l3- UNTANNED EMULSION TRANSPARENT SUPPoRT R REcEIvING LAYER F|G 3 I3 28 \\\\\\\\:\\\\L\\\\;\SUBB|NG LAYER TRANSPARENT SHEET l 4 F G TRANSFERRED EMULSION DEvELoPED BY HEAT I-IoT RoLLER 26 R cEIvING SHEET R R E T .QB'EEE TRANSFERRED EMuLsIoN BEING ExPoSED o) ExPosING LIGHT I4 25 24 TANNED NEZGATIVE 22 V A7 /I/ JVX/ 71/ A? \IO IG W 23 UNTANNED EMULSION RESIDUES OF UNTANNED LEVEL SURFACE BEING TRANSFERRED To EMuLsIoNSouRcE OF REcEIvING sI-IEET SUBSEQUENT PRINTS UNTANNED EMULSION STRATUM OF TRANSFERRED EMULSION EDWARD C. YACKEL HERBERT B. COWDEN IN V EN TORS ATT NEYS United States Patent O 7 3,232,756 COLLOID TRANSFER PROCESS Edward C. Yackel and Herbert B. Cowden, Rochester, N.Y.,assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey 7 Filed Aug. 20, 1962, Ser. No. 217,831 10 Claims. (Cl. 96-28) emulsion layer which'may contain a=gelatin=tanning.silver' halide developing agent" as well as 'a non-tanning silver halide developing agent; Upon activation of the'exposed emulsion with an alkaline solution in the presence of the developing agent or agents,tanning development of the more exposed regions" of the emulsion occur-s corresponding to thehi-ghligl'its Ofth subject, although some developrnent of the less exposed regions also takes place to provide visual density for the tr an'sfer r'ed image as explained in more detail iri U.S.- 2,716,059 above;

The developed emulsion is pressed into contact with an absorbent receiving sheet such as paper to cause the less exposed regions, and thus the less developed regions,

of the emulsion toadhere to the receiving-sheet. Sub:

sequently, when the emulsion and -receiving sheet are sep' arated, a stratum of theless exposedr'egionsof' the'emulsion remains On the sheet and appears as a positive silver image of the original subjects.

The alkaline solution which has been used for activation of the exposed emulsion layer has contained a gelatin softening agent to facilitate tran'sferof the less exposed portioris ofthe emulsion to the receiving sheet. Urea and certain other gelatin softening agents have been used-for this purpose;

In addition, sodium carbonate'has been used as an alkaline component of the alkaline solution used for initiating development of the exposed emulsion.

It has been desired to have a transparent sheet foruse as a receiving sheet in the colloid transfer process. For

instance, such a transparent receiver sheet could be used in making copies for use with a projector which will project positive transparencies of an original onto a screen. In the past, such transparencies had to be prepared by inking or drawing the desired replica upon a matte surface and then projecting it.

One suggested solution to the problem of a transparent receiving sheet' involves the use of colloidal silica dispersed in a binder such as cellulose acetate on a transparent support which might be cellulose triacetate or the like. However, when this type of transparent receiving sheet is used, the resulting image is not of satisfactory density, since the transferred gelatin does not adhere as well as to normally used paper receiving sheets.

We have found a method of making a transparent receiving sheet which not only provides a satisfactory surface for adhering the unhardened transferrable colloid image but which also results in an improved density of the image.

One object of this invention is to provide a simple photographic colloid transfer process for obtaining an image on a transparent support.- Another object is to provide a transparent support which can be used in com- 3,232,756 Patented Feb. 1, 1966 provide a coating for a transparent support which will be receptive to the adhesion of the transferrable colloid portion when used with the colloid transfer process. A still further object is to provide a coating for a transparent receiving sheet which results in an improved density of the image so that it can be used for projection purposes. Other objects will become apparent from the following description of our invention.

Our invention may be better understood by reference to the accompanying drawing wherein FIGURE 1 shows, in cross-sectional view, the appearance of a silver halide emulsion bearing support after exposure to a subject and development in the presence of a tanning developer.

FIGURE 2 shows, in enlarged cross-sectional view, theappearance of the transferred untanned emulsion image stratum in printing relation to the element of FIGURE 1.

FIGURE 3 shows, in enlarged cross-sectional view, a transparent receiving sheet which is identified as the transparent support shown in FIG. 2.

FIGURE 4 is a diagrammatic sectional view of typical apparatus, materials and methods used in our invention.

Our invention will now be described in greater detail with reference to the accompanying drawings.

In the preferred embodiment of our invention, the

substantially unhardened light-sensitive, preferably pig merited, gelatino-silver-halide emulsion layer is exposed to an object and developed in the presence of a tanning developing agent incorporated into the emulsion layer. After exposure and development, the processed photographic element appears as shown in FIGURE 1 where,

in enlarged cross-sectional view, layer it) is a film, paper or other support to which'is afiix'ed the exposed and tanning developed silver halide emulsion layer 11 contain ing the-silver and tanned gelatin image 12.

Next the moist element of FIG. 1 is placed in contact with the'transparent receiving sheet'13 of FIG. 2 and by means of pressure and, if desired, the application of heat,

the unexposed and untanned portion 16 of layer 1 1 is' causedto adhere to the transparent support 13.

By rewetting the \balance of image 16 on support 10 with the alkaline solution, additional transfers can be made.

FIGURE 4 illustrates a method of making prints by this process wherein the transparent sheet 13 is contacted with the tanned negative image in layer 11 and passed around hot roller 26 in order to increase the density of the image. The exposing light24 at point 25 also improves the density of the image.

Since the coating of our invention renders transparent supports receptive to colloid transfer, various transparent supports may be used, such as glass or any of a number of transparent polymeric materials, including cellulose esters, polystyrene, polyethylene terephthalate, or the like.

In our preferred embodiment, a transparent sheet of sheet, the image can be increased in density by exposing the receiving sheet to a photoflood lamp or to some other suitable source of radiation.

It will be appreciated that many of the transparent polymeric materials may require an additional surface treatment in order to obtain adherence of a subbing or coating composition. For instance, polyolefins, polyesters,

and the like, can be treated by electronbombardment oxidation, chlorination, and the like, to improve the surface characteristics.

The colloid layer coated on the transparent support for reception of the image has been found to be critical, since many coatings will not result in a satisfactory image transfer, particularly if the material is not sufficiently absorbent. Moreover, if the colloid is too soluble in the activator solution, it tends to dissolve during contact with the exposed matrix with the resultant transfer of the colloid to the matrix. For instance, gelatin layers which are hardened with formaldehyde are usually not absorbent enough, while most .gelatins are too soluble when coated unhardened. Moreover, bone and calf skin gelatins are too soft when coated unhardened and not absorbent when hardened by the usual methods. In addition, the sodium salts of ethyl cellulose phthalate or the sodium salt of the lactone of an interpolymer of vinyl acetate and maleic anhydride have not been found to he useful since they are too soluble.

We have found that pig gelatin can be used and also the ammonium salts of ethyl cellulose phthalate and the ammonium salts of the lactone of the interpolymer of vinyl acetate and maleic anhydride can be used. A further treatment may be used to prevent loss of ammonia from the ammonium ethyl cellulose 1phthalate salts and from the ammonia salt of the carboxy ester-lactones of an interpolymer of vinyl acetate and maleic anhydride which might cause these layers to become too insoluble so that insufiicient water is absonbed and the materials lose their ability to accept a transfer. The coating can be heated such as by drying the coating at a high temperature. For instance, a temperature range of 220-240 F. may be used with ammonium ethyl cellulose phthalate. The surface may be treated with acid solutions, which convert the surface stratum of the coating to the impervious acid form of the colloid which seals the ammonia of the lower strata in the layer. The acid is not critical and dilute hydrochloric or acetic acid solutions as low as 2.5% concentration may be applied in an amount of about 3-4 nil/sq. ft. The concentration is not critical since the acid is volatilized when the coating is dried. The carboxy ester-lactone is a water-soluble salt of a carboxy ester-lactone of an interpolymer of maleic anhydride and vinyl acetate as described in US. Patent 3,007,901 of Louis M. Minsk, reacted with an aliphatic alcohol in such a ratio as to provide a polymer containing a carboxyl content between about 3.5 and 6 milliequivalents per gram of polymer and preferably between 4.5 and 5.5 milliequivalents per gram. The salt is then 2598% neutralized with ammonia. A typical coating is disclosed in Sterman and Minsk US. patent application Serial No. 201,808.

The sodium or ammonium salt of a copolymer of ethyl acrylate and acrylic acid may also be used. In our preferred copolymer a 75% ethyl acrylate-25% acrylic acid proportion is used, but other proportions may be used. Conventional polymerization processes such as emulsion polymerization and the like may be used to prepare the copolymer.

The use of a matting agent such as silica of colloidal size or larger is not necessary to make these receiving materials work effectively, but it can be added to improve the latitude of the copying process with regard to exposure, activator temperature, and activator exhaustion. Another advantage obtained from the incorporation of matting agents is the ability to write with pencil or ballpoint .pen on the matted surfaces. Silica having a particle size ranging from about 3-30 microns in diameter are operative, but the preferred range is about -15 microns.

The thickness of the coated layers on these transparent receiving sheets may be from about 100 mg. of colloid per sq. ft. to one gram per sq. ft.

Our preferred thickness range is 250400 mg. per sq.

The following examples are intended to illustrate our invention but not to limit it" in any way.

Example 1 A 5.5% solution of the ammonium salt of ethylcellulose phthalate containing 0.20% thiourea and having pH=7.6 was coated on a transparent cellulose ester film support (subbed side) at 7.3 g. solution per sq. ft., and dried to give a layer having 400 mg. colloid per sq. ft. When used as a receiver for the colloid transfer image, dense black transfers were obtained which projected well on the Vu-Graph projector.

NOTE.This sample of ethylcellulose phthalate contained 21.8% combined phthalyl and 1.6% free phthalic acid; its viscosity at 3% concentration in ethyl alcohol/isopropanol/n-butanol 7020-10% was 4 cps. at 25 C.

Example 2 A solution like that used in Example 1 except that the thiourea was omitted and coated at the same coverage and set to a firm jelly by warming to about 60 C. In this condition, the coated layer was passed once through a 5% solution of acetic acid, and then dried as before. This material gave an excellent quality transfer when freshly made, and also after having been incubated for 14 days at 120 F., 35% RH.

Example 3 A 4% solution of ammonium salt of a carboxy esterlactone of an interpolymer of vinyl acetate and maleic anhydride in 1:1 acetone-water and containing 0.25% thiourea and 0.2% Syloid 404 (a silica dispersion) was coated at 10 g. per sq. ft. on the subbed side of a transparent cellulose ester film support and dried to give a layer having 400 mg. colloid per sq. ft. When dry, this sample was overcoated with 5% acetic acid applied at 3.5 g. per sq. ft., and again dried. This element used as a receiver with a colloid transfer matrix :gave an excellent quality image of good density; after 28 days incubation at 120 F., 35% RH, the material would still accept a high quality transfer.

Example 4 A 5% solution of high jelly strength pigskin gelatin containing 0.25% thiourea'and 0.20% Syloid 404 was coated at 8 g. per sq. ft. on the subbed side of a transparent cellulose ester film support and dried to give a layer having 400 mg. gelatin per sq. ft. This element used as a receiver for a colloid transfer matrix gave a very high quality image of high density. Samples of this material incubated for 28 days at 120 F, 35% RH. still accepted a high quality image of excellent density.

To facilitate drying, an alcohol-Water solution can be utilized.

Example 5 Two coatings were made similar to the one described in Example 4 except Dimedone was added to the pig gelatin coating solution in sufiicient quantities to give 2 and 5 mg. of Dimedone per sq. ft. After 3 months aging, the coatings containing the Dimedone gave a better.quality transfer than the coatings without the Dimedone. Best results are obtained with coatings containing 0.5- 10 mg. Dimedone per sq. ft.

Dimedone is described in US. Patent 2,944,899 as 5, 5-dimethylcyclohexanedione-1,3

Example 6 A sample of the ammonium salt of a copolymer of ethylacrylate and 25% acrylic acid containing 8.29% solids was diluted to 2.0% solids with Water and coated on a transparent cellulose ester film support at a Wet thickness of 0.005 inch. After drying, the coating was cured in an oven for 5 hours at C. This element gave good transfers from colloid transfer matrices.

The alkali metal salts of the copolymer are operative and can be used without a stabilizing step.

The coating for the transparent support may also contain an agent which increases the density of the transferred image. For instance, a silver halide fogging agent (that is, a compound which renders silver halide developable in the absence of light), thiourea, thioacetamide, dithioxamide, and dithiobiuret, thiosemicarbazide, or a soluble sulfide may be used. A compound which retards the tanning of gelatin in the presence of fogged silver halide and the gelatin tanning agent may also be incorporated in the coating, for example, sodium formaldehyde bisulfite, sodium formaldehydesulfoxalate, 2,4-dihydroxybenzoic acid, sodium benzene sulfinate, borophosphate, aminomethanesulfuric acid, or borax.

It will be appreciated that the coatings may be surface applied or that the sheet can be surface coated or coated using any of the known coating methods, such as hopper coating, wick, kiss roll, knife, and the like.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove and defined in the appended claims.

We claim:

1. In a process of photographic reproduction which comprises forming by exposure to a two-tone subject and development in a light-sensitive, substantially unhardened, organic colloid-silver halide emulsion layer, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehye per pound of gelatin freshly coated, the step of pressing the emulsion layer while said emulsion is moist against a nonfibrous, transparent polymeric sheet having thereon a non-light-sensitive coating selected from the class consisting of pig gelatin, the ammonium salt of ethylcellulosephthalate, the ammonium salt of a carboxy ester-lactone of an interpolymer of maleic anhydride and vinyl acetate and the alkali metal and ammonium salts of a copolymer of ethylacrylate and acrylic acid, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a t5 stratum of the unhardened colloid portion of said layer to said sheet.

2. The process of claim 1 in which the coating on the transparent support is pig gelatin.

3. The process of claim 1 in which the coating on the transparent support is the ammonium salt of ethylcellulosephthalate.

4. The process of claim 1 in which the coating on the transparent support is the ammonium salt of a carboxy esterlactone of an interpolymer of maleic anhydride and vinyl acetate.

5. The process of claim 1 in which the coating on the transparent support is an alkali metal salt of a copolymer of ethylacrylate and acrylic acid.

6. The process of claim 1 in which the coating on the transparent support is the ammonium salt of a copolymer of ethylacrylate and acrylic acid.

7. The process of claim 1 in which the coating on the transparent support contains 0.5-1.0 milligram per square foot of 5,S-dimethylcyclohexanedione-1,3.

8. The process of claim 1 in which the coating on the transparent support contains a matting agent.

9. The process of claim 1 in which the coating on the transparent support contains a fogging agent.

10. The process of claim 1 in which the coating on the transparent support contains silica and thiourea References Cited by the Examiner UNITED STATES PATENTS 2,576,921 12/ 1951 Buscher 117164 2,596,756 5/1952 Yutzy et al. 96-28 2,858,238 10/1958 Brown 117-464 2,865,745 12/ 1958 Chan et al. 9628 2,944,899 7/1960 Damschrader et al. 9695 2,992,213 7/1961 Gates et al. 9687 3,043,688 7/1962 Weyerts et al. 9628 3,060,023 10/1962 Burg et al. 9687 3,062,674 11/1962 Houck et al. 9687 3,072,482 1/1963 Beeber et al. 9 7 3,080,230 3/1963 Haydn et al. 96 -28 3,108,995 10/ 1963 Tourtellotte et al. 96111 X NORMAN G. TORCHIN, Primary Examiner. 

1. IN A PROCESS PF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES FORMING BY EXPOSURE TO A TWO-TONE SUBJECT AND DEVELOPMENT IN A LIGHT-SENSITIVE, SUBSTANTIALLY UNHARDENED, ORGANIC COLOID-SILVER HALIDE EMULSION LAYER, A HARDENED COLLOID IMAGE AND LEAVING SUBSTANTIALLY NHARDENED COLLOID IN THE REMAINING AREA OF SAID LAYER, SAID UNHARDENED LAYER BEING NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYE PER POUND OF GELATIN FRESHLY COATED, THE STEP OF PRESSING THE EMULSION LAYER WHILE SAID EMULSION IS MOIST AGAINST A NONFIBROUS, TRANSPARENT POLYMERIC SHEET HAVING THEREON A NON-LIGHT-SENSITIVE COATING SELECTED FROM THE CLASS CONSISTIG OF PIG GELATIN, THE AMMONIUM SALT OF ETHYLCELLULOSEPHTHALATE, THE AMMONIUM SALT OF A CARBOXY ESTER-LACTONE OF AN INTERPOLYMER OF MALEIC ANHYDRIDE AND VINYL ACETATE AND THE ALKALI METAL AND AMMONIUM SALTS OF A COPOLYMER OF ETHYLACRYLATE AND ACYLIC ACID, TO CAUSE ONLY SAID UNHARDENED COLLOID PORTION OF SAID LAYER TO ADHERE TO SAID SHEET, AND SEPARATING SAID SHEET AND SAID EMULSION LAYER TO TRANSFER ONLY A STRATUM OF THE UNHARDENED COLLOID PORTION OF SAID LAYER TO SAID SHEET. 